Embodiments of the present disclosure relate to a longitudinal piston-engine cylinder head having a cylinder head body and a base plate comprising at least one element, the base plate being interposed between a combustion chamber and the cylinder head body, comprising an upper face facing the cylinder head body and an opposing lower face arranged to face the combustion chamber and attached to the cylinder head body.
It also relates to a base plate, a base plate element and an assembly including a piston-motor cylinder head with such a base plate.
It also relates to a method for assembling a cylinder head body with such a base plate by screwing.
It can be used particularly, but not necessarily exclusively, in the domain of compact engines having reduced mass, high power density (ratio between the mechanical power supplied by the engine and the total volume corresponding to the maximum swept volume of the piston), and very high thermodynamic efficiency, in particular for an aircraft or a racing car.
Improving the efficiency of the thermodynamic cycle of a piston engine, regardless of the cycle chosen (Carnot, Stirling, diesel, etc.), is an ongoing concern for engine manufacturers.
Engine efficiency depends on compression and the energy intake in the combustion chamber, and more specifically the maximum respective temperature and pressure values that can be reached therein.
It is known to increase pressure by supercharging the combustion chamber with oxidant (air).
Nonetheless, this technique involves a compromise between pressure inside the chamber and engine weight.
Indeed, to achieve high pressures and the combustion temperature of the fuel, materials that can mechanically withstand these pressure and temperature conditions need to be used and/or the dimensions of the parts need to be adapted to the material chosen.
This type of material, such as steel or cast iron, is heavy (mass density greater than 5000 kg/m3).
To overcome this drawback, an engine including an engine block made of a strong material and a cylinder head made of a lighter material has been proposed.
However, in this case, the cylinder head has a side facing the combustion chamber that is made of relatively weak materials, which limits the potential of the engine.
A cylinder head made of two parts of different materials that are welded together is also known (EP 0262240).
Such a cylinder head nonetheless has drawbacks.
Indeed, such a cylinder head cannot operate in high pressure and temperature ranges, in particular if the thickness of the base plate is reduced in order to limit weight.
Such a cylinder head is not simple or reversible to assemble and requires the two parts of different materials to be welded together, which is also complex and costly.
Finally, the parts must be perfectly shaped since the slightest dimensional defect would result in a significant loss of efficiency.
A device made of two different materials but that has low resistance to vibration and uses an adhesive layer between the materials is also known (WO 03/062621).
Document DE 2514592 describes a two-part single-cylinder cylinder head with a cooling chamber that is liable to corrosion problems.